Sprinkler heads designed for ceiling and/or wall mounting within a structure are offered in a wide range of sizes, shapes and styles. Internally, the actual mechanisms which result in the release of water (or other liquid) can vary from the sophisticated (and expensive) electronic systems to the less expensive mechanical systems.
Some of the mechanical systems employ the use of a shape-memory alloy (SMA) for fabrication of one or more of the component parts. The design theory associated with the use of this type of SMA material is that it undergoes a change of shape when heated. This type of SMA material may also be referred to as “memory metal”. This temperature-based movement which is a characteristic of SMA material can be utilized within a sprinkler head mechanism in order to effect a desired operational or performance result. One use of SMA material in a sprinkler head is as a release component. The typical construction is such that at an elevated temperature the SMA component opens up or expands in some fashion which in turn allows the release of another component. It is the release of this other component which opens the flow path for the liquid. As one example of this type of construction, see the disclosure of U.S. Pat. No. 5,494,113 which issued Feb. 27, 1996.
Another use of SMA material in a sprinkler head is as a catalyst for the fracture of another component. One such example of this use of SMA material is found in US2015/0266141, published Sep. 14, 2015. Described in this published patent application is a temperature-sensitive actuator which includes a frangible bolt and a shape-memory element. The frangible bolt and the shape-memory element are coupled together in such a way that expansion of the shape-memory element may result in breaking of the frangible bolt.
Each of these uses for SMA material for a component part of a sprinkler head has a feature in common. This feature in common is described as being “irreversible”. In the first example, once the locating member 58 and control lever 62 fall, there is no automatic mechanism to restore or return these components to their starting positions, prior to the “fall”. That particular sprinkler head must be replaced, repaired or reworked in some fashion if it is going to be reused. However, this structure is not automatically reusable as these two components are not moved back to their starting positions automatically. In the second example, once the frangible bolt breaks, that fractured status cannot be reversed. The sprinkler head must be serviced and the frangible bolt must be replaced in order to restore the sprinkler head to its starting or original condition.
In view of the above it would be an improvement for sprinkler head designs which use SMA material if the consequences of an elevated temperature could be automatically reversed and the initial starting condition of the structure restored when the elevated temperature is removed and near standard or normal (ambient) conditions are reestablished. It would also be an improvement for sprinkler head designs using SMA material to have a simpler design with fewer component parts and component parts of less complexity.
The exemplary embodiments of the present invention are directed to providing one or more improvements to the design and functioning of mechanical sprinkler heads.